A strut-type suspension (McPherson strut) used for a front wheel of an automobile has structure in which a strut assembly comprising a piston rod and a hydraulic shock absorber is combined with a coil spring. When a steering is operated, the strut assembly is rotated together with the coil spring. Accordingly, to allow smooth rotation of the strut assembly, usually a bearing is placed between an upper mount which is a mounting mechanism for mounting the strut assembly onto the automobile body, and an upper spring seat that is a spring seat for the upper end of the coil spring.
For example, the Patent Literature 1 discloses a sliding bearing made of synthetic resin, as a bearing for a strut-type suspension. This sliding bearing comprises: an upper case made of synthetic resin which is installed on the side of an upper mount; a lower case made of synthetic resin which is installed on the side of an upper spring seat and is combined rotatably with the upper case; and an annular center plate made of synthetic resin which is placed in an annular space formed by combining the upper case with the lower case and realizes smooth rotation between the upper case and the lower case.
Here, the center plate is a ring member having an L-shape in cross-section, comprising: a ring portion which has a surface in which a thrust bearing surface is formed; and a cylindrical portion which connects to an inner peripheral edge of the back surface of the ring portion, and has an inner peripheral surface in which a radial bearing surface is formed. Further, the upper case has: an annular thrust load transmission surface which slides on the thrust bearing surface which is formed in the surface of the ring portion of the center plate; and a cylindrically-shaped radial load transmission surface which is inserted into the cylindrical portion of the center plate and slides on the radial bearing surface which is formed in the inner peripheral surface of the cylindrical portion of the center plate.
The sliding bearing having the above structure supports the load in the thrust direction applied to a strut-type suspension by the thrust bearing surface which is formed in the surface of the ring portion of the center plate, via the thrust load transmission surface of the upper case. On the other hand, the sliding bearing supports the load applied to the strut-type suspension in the radial direction by the radial bearing surface which is formed in the inner peripheral surface of the cylindrical portion of the center plate, via the radial load transmission surface of the upper plate.